The invention relates to an open-end spinning rotor assembly having a rotor and a rotor shaft, the free end of which rotor shaft is provided with an exchangeable supporting element which is assigned to a step bearing.
In practice, open-end spinning rotors are used today in rotor spinning machines, the shaft of which is a one-piece component which has no supporting element on its end. Although it is known to mount supporting elements on the free end of the spinning rotor shaft, these solutions are not used in practice. It is known, for example, on the basis of the German Patent Document DE-A 27 16 573, FIG. 3, to mount a pin-type projection on the shaft end which penetrates into a step bearing housing.
From the German Patent Document DE-A 19 01 453, FIG. 26, it is known to mount on the free front face of the shaft of an open-end spinning rotor a supporting element made of hard metal, of a diamond, or a ceramic material which, under certain circumstances, should also be exchangeable. This supporting device has a semispherical design.
The spinning rotors used today rotate at very high rotational speeds which are above 100,000 min.sup.-1. The rotors of these open-end spinning rotor assemblies, which previously were worn out relatively fast, have been improved so much that they permit a relatively long period of usability which is considerably extended in comparison to the previous period of usability. It was found that under these conditions--a high rotational speed of the rotor, on the one hand, and a long durability of the rotors, on the other hand--wear occurs on the end of the rotor shaft assigned to the step bearing. This wear results in a shortening of the shaft and thus to a change of position of the rotor. Although it is possible to correct this change of position by an adjusting of the step bearing, this correcting is not very suitable for practical operations. The reason is that in practice there is the requirement that the open-end spinning rotors of the individual spinning points of a machine are to be exchangeable with one another. It is therefore not practical to individually adjust the position of the open-end spinning rotors. The expenditures of reusing the rotor and exchanging the shaft are high so that today the whole open-end spinning rotor assembly, that is, the rotor and the shaft, are used as exchangeable parts, the durability of which is predominantly determined by the wear of the rotor shaft. The known suggestions concerning possibly exchangeable supporting elements at the end of the rotor shaft also require expenditures which are so excessive that they are no longer economical.
It is an object of the invention to provide exchangeable supporting elements for open-end spinning rotors of the initially mentioned type which can be exchanged easily so that it makes sense economically.
This object is achieved according to preferred embodiments of the invention in that the supporting element has a centric guiding surface which is assigned to a guiding surface of the shaft which is concentric with respect to the shaft axis, and the axial length of which is larger than half the overall axial length of the supporting element.
In this case, the invention is based on the recognition that an exchanging of supporting elements will result in lower costs and therefore be economical only if the exchange is carried out in such a manner that, after an exchange, there will be no impermissible unbalanced masses which lead to an additional balancing of the whole open-end spinning rotor assembly. This idea is implemented in that relatively long guiding surfaces are provided by which the supporting element is connected with a rotor shaft. As a result, there is a low risk from the start that, because of the exchange of the supporting element, ovalization occurs which results in unbalanced masses.
In a further development of the invention, it is provided that the guiding surface of the supporting element with respect to the guiding surface of the shaft is dimensioned such that the two guiding surfaces together form a press fit. On the one hand, this type of a connection is easy to establish while, on the other hand, in addition, the possibility is excluded that the risk of unbalanced masses is increased because of fastening devices.
In order to facilitate the exchange of the supporting element, it is advantageous for the supporting element, in a further development of the invention, to be provided with an essentially radial application surface for a pull-off tool. This permits a simple and fast demounting of the worn-out supporting element.
In a further development of the invention, it is provided that the supporting element is provided with a stop surface which is assigned to a stop of the shaft. This ensures that axial loads do not cause the supporting element to change its position relative to the shaft whereby the position of the rotor plate may again be changed in an impermissible manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.